These circuit arrangements and methods are known for example from DE 197 33 560 A1 and DE 101 20 143 A1.
In modern internal combustion engines, the control of the injection of fuel usually takes place with the help of electronic engine control devices, which actuate the injection valves in a suitable manner, so that injection nozzle bores are cleared at desired points in times by the movement of valve bodies such as nozzle needles and fuel injections take place in a combustion chamber. The more exact the movements of the valve bodies can be controlled or reproduced, the better results can be achieved regarding the engine characteristics such as performance, fuel consumption and pollutant emission level. Furthermore, tolerances regarding the above-mentioned engine characteristics can be reduced by regulating the valve body movement. A need exists therefore for the valve body movement or the position of the valve body to be detected relative to a valve seat of the fuel valve.
DE 34 45 721 A1 discloses an electrically actuable magnetic valve suitable for injecting fuel. This known magnetic valve comprises a contact switch formed of a valve body and an associated valve seat, the switching state of which thereby representing the position of the valve body relative to the valve seat. For the detection of the switching state of this on-off switch, the magnetic valve is supplied with a measuring voltage via a resistor, and the voltage drop generated at the resistor is measured. When the valve is closed, a current flows over the resistor and generates a voltage drop. However, when the valve is opened, the electrical connection between the valve body and the valve seat is interrupted, so the current flow and consequently the voltage drop at the resistor becomes zero.
DE 103 19 329 A1 discloses an injection valve which is driven for example in a piezoelectric manner, which comprises a double switch for the detection of the position of the valve body relative to the valve seat, which double switch consists of a seat contact switch (similar to the contact switch described in DE 34 45 721 A1) and additionally a limit switch, so that not only the start and the end of the movement of the valve body can be sensed during an injection, but additionally the start and the end of a valve body limit stop. These points in time which are sensed additionally correspond to the attainment of a fully open degree and the start of a reduction based on this fully open degree of the valve. The accuracy of the information regarding the position of the valve body is thereby increased.
The provision of the known contact switch for the detection of the valve position means a certain amount of additional work in the region of the fuel valve, especially as the durability or the life of these contact switches has to be ensured hereby during a use in series engines.